As President Obama put it today in a news conference with Ms. Park, "We can reconsider the 2015 timeline for transferring operational control for our alliance.”

Although generals would normally be expected to want to be in full command of their own troops, South Korean officials have balked at the concept of shifting wartime command for years.

During the Korean War, the US took over all allied forces in South Korea under the aegis of the United Nations Command, with the agreement of then-President Syngman Rhee. American generals then assumed overall command of the massive effort needed to throw back first the North Koreans and then the Chinese. The US returned peacetime control of South Korean forces in 1994.

Negotiators from the US and South Korea have been discussing for years when and how to get the South Koreans to take over wartime command of all their troops as well. But both US military analysts and South Korean defense officials have argued that the country was not in the position to take over all the complicated overall command responsibilities.

South Korean generals agree with this assessment, saying they were not quite ready to work out all the arrangements needed to ensure the defeat of whatever forces the North Koreans might muster against them.

Neither Obama nor Park hinted at how long they would like to postpone the transfer of operational control. But a driving factor was the worry that North Korea may be developing nuclear warheads and long-range missiles with which to deliver them to targets more rapidly than expected. South Korean intelligence has warned that the North may be preparing for a fourth nuclear test soon. (Some dismiss this threat as typical bluster by Pyongyang.)

The decision to reconsider the timing of the transfer comes nearly a year after Obama's statement that the two countries were "on track" for South Korea to "assume operational control for the alliance in 2015." He made the remarks during a visit to Seoul last May.

The reversal of that decision means that US and South Korean generals will attempt to agree on a new date later this year. South Korea is expected to push for putting it off as long as possible, arguing that it not only lacks the military strength needed to exercise command independently, but also expects further escalation of tensions in the region.

Aside from North Korea's nuclear and missile programs, China's steady increase in military strength is a matter of concern, despite repeated Chinese calls for "stability" on the Korean peninsula.